Automatic nail guns, powered by compressed air or electricity, are used, for example, to attach roofing material, such as tarpaper, to the roof of a house. A generally flat cap is often used with each nail. A nail penetrates the cap and the tarpaper and protrudes into the underlying roof structure, attaching the roofing material to the roof surface.
Typically, an operator must manually place and hold a cap under the nose of a nail gun and then trigger the gun to drive a nail though the cap into the roof structure. The manual placement of caps presents a serious safety hazard to the operator because the operator's hand is close to the nose of the gun when a nail is driven through the nose of the gun. In addition, manual placement of caps is time-consuming and inefficient.
A cap feeding device may be employed to reduce the risk associated with manual placement of caps and to improve the efficiency of roofing operation. The cap feeding device automatically places a cap under the nose of a nail gun, and then the nail gun drives a nail through the cap and into the underlying roof structure.
A conventional cap feeding device generally includes a cap container and a base having a channel. The base extends between the cap container and a position under the nose of the nail gun. Caps are fed into the channel of the base from the cap container and pushed to the position under the nose of the nail gun. When the gun is triggered, a nail penetrates and dislodges the cap under the nose of the nail gun and protrudes into the underlying roof structure. The feeding of the caps under the nose of the nail gun is coordinated with the ejection of the nails through the nose of the nail gun, so that a cap is placed under the nose of the gun before the gun is triggered to expel a nail.
Conventional cap feeding devices have a number of drawbacks. For example, conventional cap feeding devices are generally heavy, putting additional stress on the operator's hand holding the nail gun. Also, many conventional cap feeding devices can only be installed close to the front end of a nail gun, making the nail gun not only heavy but also unbalanced with most of the weight placed at the front end of the gun. This makes the nail gun difficult to handle and may put stress on the operator's hand and wrist. In addition, with so many components placed near the nose of the gun, it is difficult to see the position of the nose of the gun, making a precise placement of a nail difficult.
The conventional cap feeding devices are installed close to the front end of the gun because designers need to place a conventional cap container close to the nose of the gun to reduce the weight of the cap feeding device. The reason is that in many devices a cap is pushed directly from the cap container to a position under the nose of the nail gun. Thus, if the cap container is far from the nose of the gun, a long shuttle is needed to push a cap from the container to the position under the nose of the nail gun through the channel of the base. In addition, an actuator, such as an air cylinder, with a long displacement is also needed to drive the shuttle. The displacement of the actuator should be about the same as the distance between the cap container and the nose of the nail gun. A long shuttle and actuator increase the weight and size of the cap feeding device. With the cap feeding device placed near the nose of the gun, the shuttle and actuator, thus the cap feeding device, can be made lighter, smaller and less expensive.